Experimental investigation on test methods for mode II interlaminar fracture testing of carbon fiber reinforced composites

Abstract In this paper, experimental investigation on the test methods for mode II interlaminar fracture testing of carbon fiber reinforced composites are carried out. Mode II interlaminar fracture testing of unidirectional composite of carbon fiber reinforced epoxy (T800/#3631) are conducted using four kinds of test methods, namely end notched flexure (ENF) test, end loaded split (ELS) test, four-point bend end notched flexure (4ENF) test, and over notched flexure (ONF) test. An analytical model based on a point-friction assumption and classical beam theory is proposed to evaluate the effect of friction between crack faces on the mode II interlaminar fracture toughness in the 4ENF and ONF tests. The analytical model is validated by the comparison of analytical results with previous ones obtained from finite element analysis. Experimental results show that the ENF test gives reliable initiation value of fracture toughness with a small scatter and that the average value of fracture toughness obtained from 4ENF test is about 2% higher than that obtained from the ENF test. The effect of friction in the 4ENF test is much lower than that in the ONF test in which the effect of friction increases with the crack growing. It is concluded that the 4ENF test method is an effective test method for the experimental evaluation of mode II propagation interlaminar fracture toughness of carbon fiber reinforced composites.

[1]  J. G. Williams,et al.  Fracture Mechanics Testing Methods for Polymers, Adhesives and Composites , 2001 .

[2]  C. Sun,et al.  Effect of compressive transverse normal stress on mode II fracture toughness in polymeric composites , 2007 .

[3]  Barry D. Davidson,et al.  Mode II fracture toughness evaluation using four point bend, end notched flexure test , 1999 .

[4]  James M. Whitney,et al.  A Double Cantilever Beam Test for Characterizing Mode I Delamination of Composite Materials , 1982 .

[5]  J. Eisenmann,et al.  Characterizing delamination growth in graphite-epoxy , 1982 .

[6]  L. Ilcewicz,et al.  Mode I Interlaminar Fracture Toughness of Composites Using Slender Double Cantilevered Beam Specimens , 1985 .

[7]  Anthony J. Kinloch,et al.  The analysis of interlaminar fracture in uniaxial fibre-polymer composites , 1990, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[8]  Wesley J. Cantwell,et al.  Measurement of initiation values of GIC in IM6/PEEK composites , 1989 .

[9]  Y. Takao,et al.  Improvement of the interlaminar fracture toughness of composite laminates by whisker reinforced interlamination , 2002 .

[10]  W. X. Wang,et al.  The Interlaminar Mode I Fracture of IM7/LaRC-RP46 Composites at High Temperatures , 1998 .

[11]  Barry D. Davidson,et al.  Effects of Friction, Geometry, and Fixture Compliance on the Perceived Toughness from Three-and Four-Point Bend End-Notched Flexure Tests , 2005 .

[12]  Andreas J. Brunner,et al.  Mode II fracture testing of composites: a new look at an old problem , 2006 .

[13]  Xuekun Sun,et al.  Numerical evaluation of the effects of friction and geometric nonlinearities on the energy release rate in three- and four-point bend end-notched flexure tests , 2006 .

[14]  Peter Davies,et al.  A status report on delamination resistance testing of polymer-matrix composites , 2008 .

[15]  Barry D. Davidson,et al.  A Direct Energy Balance Approach for Determining Energy Release Rates in Three and Four Point Bend End Notched Flexure Tests , 2005 .

[16]  A. Morais,et al.  Application of the effective crack method to mode I and mode II interlaminar fracture of carbon/epoxy unidirectional laminates , 2007 .

[17]  M. Kikuchi,et al.  Stabilized End Notched Flexure Test: Characterization of Mode II Interlaminar Crack Growth , 1991 .

[18]  Barry D. Davidson,et al.  Evaluation of the accuracy of the four-point bend end-notched flexure test for mode II delamination toughness determination , 2000 .